The clinical features, arteriographic findings, and treatment of 81 patients with spinal arteriovenous malformations demonstrated that there are distinguishing clinical features in patients with arteriovenous malformations of the spinal cord compared to those of patients with arteriovenous fistulas of the spinal dura. The findings indicate that spinal arteriovenous fistulas are acquired lesions, and not congenital, as was previously thought, and support arteriovenous malformations of the spinal cord as congenital lesions. The findings also indicate that AVMs of the spinal cord produce myelopathy as a result of high flow and that the associated arterial steal and the multiple hemorrhages experienced by these patients result from the rapid flow through the lesions, whereas patients with spinal dural AV fistulas develop myelopathy as a result of increased venous pressure in the spinal cord. Magnetic resonance imaging permits demonstration of the presence and site of arteriovenous malformations of the spinal cord and therefore is a valuable and safe, non-invasive technique to investigate patients suspected of having spinal AVMs. Laser Doppler velocimetry can be used to monitor microcirculatory flow in the brain intraoperatively in patients with cerebral arteriovenous malformations. The results from using this procedure in one such patient demonstrate that the excision of the AVM leads to a prominent increase in cerebral blood flow in the tissue adjacent to the AVM and support the presence of a transient loss of brain vasoregulation in this tissue.